For many many months now, Thunar has had an annoying bug where it suddenly freezes and becomes totally unresponsive. Finally, I found a pattern in the behavior, as it appears to be related to temporary files being created, then removed.

1) open a terminal window and enter : thunar ~/.config/xfce4/desktop/
2) move the thunar window so that it overlaps the terminal window (see attached "Before" screenshot)
2) click the desktop, then relocate one of the icons on the desktop
3) activate the terminal window
4) activate the thunar window, and notice how the window has a blank area where the terminal window overlapped (see attached "After" screenshot)

You'll have to report that upstream at xfce.org. But they'll probbably know already since it's reported and fixed on launchpad. You might check that. If it's fixed we'll have the fix in SolydX10 buster.
Remember, SolydXK is based on Debian stable which means that only bugs that compromise system security will get fixed on the current stable system. Everything else has to wait for buster (or backports if somebody thinks it's worth the time).

I feel this bug is very serious for SolydX users, since Thunar is one of the fundamental parts of our desktop environment and it freezes all the time you have it running, if something happens in the directory opened - which happens, if you actually use it for tis purpose, i.e. file management. I think there should be already workaround for this. Why, the bug is really annoying and it lasts for months!

Obviously, one is to use different file manager - I myself use Double Commander (DC) most times, but I still have use for Thunar where its better integration into DE is important - i.e. DC does not support drag'n'drop with most of the other applications, I have few useful Thunar user actions, it is needed for setting desktop-wide file associations, etc.

So does anyone have a simple and tested workaround involving Thunar upgrade or downgrade or patched version in Stretch compatible repo please?

I myself use Double Commander (DC) most times, but I still have use for Thunar where its better integration into DE is important - i.e. DC does not support drag'n'drop with most of the other applications, I have few useful Thunar user actions, it is needed for setting desktop-wide file associations, etc.

Me too. And I have never encountered any freeze in Thunar. I also don't leave it open after having completed whatever I needed it for (Thunar user action).

Stevepusser is actually a very knowledgeable guy regarding backports. You can trust his advice. Or just wait it out until buster becomes stable.